diff --git a/uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/utils/DateUtils.kt b/uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/utils/DateUtils.kt
index fd7929b87..8af545504 100644
--- a/uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/utils/DateUtils.kt
+++ b/uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/utils/DateUtils.kt
@@ -36,10 +36,15 @@ abstract class DateUtils {
         private var startDayHourOffset: Int = 0
         private var startDayMinuteOffset: Int = 0
 
+        /**
+         * Number of milliseconds in one second.
+         */
+        const val SECOND_LENGTH: Long = 1000
+
         /**
          * Number of milliseconds in one minute.
          */
-        const val MINUTE_LENGTH: Long = 60 * 1000
+        const val MINUTE_LENGTH: Long = 60 * SECOND_LENGTH
 
         /**
          * Number of milliseconds in one hour.
diff --git a/uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/utils/MidnightTimer.kt b/uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/utils/MidnightTimer.kt
index e0661ba77..903099293 100644
--- a/uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/utils/MidnightTimer.kt
+++ b/uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/utils/MidnightTimer.kt
@@ -33,31 +33,39 @@ open class MidnightTimer @Inject constructor() {
     private val listeners: MutableList<MidnightListener> = LinkedList()
     private lateinit var executor: ScheduledExecutorService
 
-    @Synchronized fun addListener(listener: MidnightListener) {
+    @Synchronized
+    fun addListener(listener: MidnightListener) {
         this.listeners.add(listener)
     }
 
-    @Synchronized fun onPause(): MutableList<Runnable>? = executor.shutdownNow()
+    @Synchronized
+    fun onPause(): MutableList<Runnable>? = executor.shutdownNow()
 
-    @Synchronized fun onResume() {
-        executor = Executors.newSingleThreadScheduledExecutor()
+    @Synchronized
+    fun onResume(
+        delayOffsetInMillis: Long = DateUtils.SECOND_LENGTH,
+        testExecutor: ScheduledExecutorService? = null
+    ) {
+        executor = testExecutor ?: Executors.newSingleThreadScheduledExecutor()
         executor.scheduleAtFixedRate(
             { notifyListeners() },
-            DateUtils.millisecondsUntilTomorrowWithOffset() + 1000,
+            DateUtils.millisecondsUntilTomorrowWithOffset() + delayOffsetInMillis,
             DateUtils.DAY_LENGTH,
             TimeUnit.MILLISECONDS
         )
     }
 
-    @Synchronized fun removeListener(listener: MidnightListener) = this.listeners.remove(listener)
+    @Synchronized
+    fun removeListener(listener: MidnightListener) = this.listeners.remove(listener)
 
-    @Synchronized private fun notifyListeners() {
+    @Synchronized
+    private fun notifyListeners() {
         for (l in listeners) {
             l.atMidnight()
         }
     }
 
-    interface MidnightListener {
+    fun interface MidnightListener {
         fun atMidnight()
     }
 }
diff --git a/uhabits-core/src/jvmTest/java/org/isoron/uhabits/core/BaseUnitTest.kt b/uhabits-core/src/jvmTest/java/org/isoron/uhabits/core/BaseUnitTest.kt
index f97991b6d..4079600ab 100644
--- a/uhabits-core/src/jvmTest/java/org/isoron/uhabits/core/BaseUnitTest.kt
+++ b/uhabits-core/src/jvmTest/java/org/isoron/uhabits/core/BaseUnitTest.kt
@@ -95,15 +95,13 @@ open class BaseUnitTest {
     }
 
     fun unixTime(year: Int, month: Int, day: Int): Long {
-        val cal = getStartOfTodayCalendar()
-        cal.set(year, month, day, 0, 0, 0)
-        return cal.timeInMillis
+        return unixTime(year, month, day, 0, 0)
     }
 
-    open fun unixTime(year: Int, month: Int, day: Int, hour: Int, minute: Int): Long {
+    open fun unixTime(year: Int, month: Int, day: Int, hour: Int, minute: Int, milliseconds: Long = 0): Long {
         val cal = getStartOfTodayCalendar()
         cal.set(year, month, day, hour, minute)
-        return cal.timeInMillis
+        return cal.timeInMillis + milliseconds
     }
 
     fun timestamp(year: Int, month: Int, day: Int): Timestamp {
diff --git a/uhabits-core/src/jvmTest/java/org/isoron/uhabits/core/reminders/ReminderSchedulerTest.kt b/uhabits-core/src/jvmTest/java/org/isoron/uhabits/core/reminders/ReminderSchedulerTest.kt
index d354e81f0..cf81fbe9a 100644
--- a/uhabits-core/src/jvmTest/java/org/isoron/uhabits/core/reminders/ReminderSchedulerTest.kt
+++ b/uhabits-core/src/jvmTest/java/org/isoron/uhabits/core/reminders/ReminderSchedulerTest.kt
@@ -138,7 +138,7 @@ class ReminderSchedulerTest : BaseUnitTest() {
         reminderScheduler.schedule(habit)
     }
 
-    override fun unixTime(year: Int, month: Int, day: Int, hour: Int, minute: Int): Long {
+    override fun unixTime(year: Int, month: Int, day: Int, hour: Int, minute: Int, milliseconds: Long): Long {
         val cal: Calendar = getStartOfTodayCalendar()
         cal[year, month, day, hour] = minute
         return cal.timeInMillis
diff --git a/uhabits-core/src/jvmTest/java/org/isoron/uhabits/core/utils/MidnightTimerTest.kt b/uhabits-core/src/jvmTest/java/org/isoron/uhabits/core/utils/MidnightTimerTest.kt
new file mode 100644
index 000000000..b92507da0
--- /dev/null
+++ b/uhabits-core/src/jvmTest/java/org/isoron/uhabits/core/utils/MidnightTimerTest.kt
@@ -0,0 +1,48 @@
+package org.isoron.uhabits.core.utils
+
+import kotlinx.coroutines.asCoroutineDispatcher
+import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.withContext
+import org.isoron.uhabits.core.BaseUnitTest
+import org.junit.Test
+import java.util.Calendar
+import java.util.TimeZone
+import java.util.concurrent.Executors
+import kotlin.coroutines.resume
+import kotlin.coroutines.suspendCoroutine
+import kotlin.test.assertEquals
+
+class MidnightTimerTest : BaseUnitTest() {
+
+    @Test
+    fun testMidnightTimer_notifyListener_atMidnight() = runBlocking {
+        // Given
+        val executor = Executors.newSingleThreadScheduledExecutor()
+        val dispatcher = executor.asCoroutineDispatcher()
+
+        withContext(dispatcher) {
+            DateUtils.setFixedTimeZone(TimeZone.getTimeZone("GMT"))
+            DateUtils.setFixedLocalTime(
+                unixTime(
+                    2017,
+                    Calendar.JANUARY,
+                    1,
+                    23,
+                    59,
+                    DateUtils.MINUTE_LENGTH - 1
+                )
+            )
+
+            val suspendedListener = suspendCoroutine<Boolean> { continuation ->
+                MidnightTimer().apply {
+                    addListener { continuation.resume(true) }
+                    // When
+                    onResume(1, executor)
+                }
+            }
+
+            // Then
+            assertEquals(true, suspendedListener)
+        }
+    }
+}